The correct answer is option 4, Neonatology. Neonatology is the study of newborn infants, specifically those up to the age of 3 months. It focuses on the medical care and development of newborns, including their physiological and behavioral characteristics. Neonatologists are specialized doctors who provide specialized care to newborns, especially those who are premature or have medical complications.

Option 1, Chorology, is the study of geographical distribution of organisms. Option 2, Conchology, is the study of shells, particularly mollusk shells. Option 3, Nematology, is the study of nematodes, which are a type of roundworm.

So, the correct option for the study of newborns up to the age of 3 months is Neonatology.